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https://issues.apache.org/jira/browse/SOLR-8323?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15279218#comment-15279218
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ASF GitHub Bot commented on SOLR-8323:
--------------------------------------
Github user dragonsinth commented on a diff in the pull request:
https://github.com/apache/lucene-solr/pull/32#discussion_r62771165
--- Diff:
solr/solrj/src/java/org/apache/solr/common/cloud/ZkStateReader.java ---
@@ -1069,32 +1100,190 @@ public static String getCollectionPath(String
coll) {
return COLLECTIONS_ZKNODE+"/"+coll + "/state.json";
}
- public void addCollectionWatch(String coll) {
- if (interestingCollections.add(coll)) {
- LOG.info("addZkWatch [{}]", coll);
- new StateWatcher(coll).refreshAndWatch(false);
+ /**
+ * Notify this reader that a local Core is a member of a collection, and
so that collection
+ * state should be watched.
+ *
+ * Not a public API. This method should only be called from
ZkController.
+ *
+ * The number of cores per-collection is tracked, and adding multiple
cores from the same
+ * collection does not increase the number of watches.
+ *
+ * @param collection the collection that the core is a member of
+ *
+ * @see ZkStateReader#unregisterCore(String)
+ */
+ public void registerCore(String collection) {
+ AtomicBoolean reconstructState = new AtomicBoolean(false);
+ collectionWatches.compute(collection, (k, v) -> {
+ if (v == null) {
+ reconstructState.set(true);
+ v = new CollectionWatch();
+ }
+ v.coreRefCount++;
+ return v;
+ });
+ if (reconstructState.get()) {
+ new StateWatcher(collection).refreshAndWatch();
+ synchronized (getUpdateLock()) {
+ constructState();
+ }
+ }
+ }
+
+ /**
+ * Notify this reader that a local core that is a member of a collection
has been closed.
+ *
+ * Not a public API. This method should only be called from
ZkController.
+ *
+ * If no cores are registered for a collection, and there are no {@link
CollectionStateWatcher}s
+ * for that collection either, the collection watch will be removed.
+ *
+ * @param collection the collection that the core belongs to
+ */
+ public void unregisterCore(String collection) {
+ AtomicBoolean reconstructState = new AtomicBoolean(false);
+ collectionWatches.compute(collection, (k, v) -> {
+ if (v == null)
+ return null;
+ if (v.coreRefCount > 0)
+ v.coreRefCount--;
+ if (v.canBeRemoved()) {
+ watchedCollectionStates.remove(collection);
+ lazyCollectionStates.put(collection, new
LazyCollectionRef(collection));
+ reconstructState.set(true);
+ return null;
+ }
+ return v;
+ });
+ if (reconstructState.get()) {
+ synchronized (getUpdateLock()) {
+ constructState();
+ }
+ }
+ }
+
+ /**
+ * Register a CollectionStateWatcher to be called when the state of a
collection changes
+ *
+ * A given CollectionStateWatcher will be only called once. If you want
to have a persistent watcher,
+ * it should register itself again in its {@link
CollectionStateWatcher#onStateChanged(Set, DocCollection)}
+ * method.
+ */
+ public void registerCollectionStateWatcher(String collection,
CollectionStateWatcher stateWatcher) {
+ AtomicBoolean watchSet = new AtomicBoolean(false);
+ collectionWatches.compute(collection, (k, v) -> {
+ if (v == null) {
+ v = new CollectionWatch();
+ watchSet.set(true);
+ }
+ v.stateWatchers.add(stateWatcher);
+ return v;
+ });
+ if (watchSet.get()) {
+ new StateWatcher(collection).refreshAndWatch();
--- End diff --
I feel like this needs to check whether or not the collection exists / is a
legacy collection. If it's a legacy collection, you don't want to try to
create a StateWatcher.
> Add CollectionWatcher API to ZkStateReader
> ------------------------------------------
>
> Key: SOLR-8323
> URL: https://issues.apache.org/jira/browse/SOLR-8323
> Project: Solr
> Issue Type: Improvement
> Affects Versions: 6.0
> Reporter: Alan Woodward
> Assignee: Alan Woodward
> Attachments: SOLR-8323.patch, SOLR-8323.patch, SOLR-8323.patch,
> SOLR-8323.patch
>
>
> An API to watch for changes to collection state would be a generally useful
> thing, both internally and for client use.
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